rbd: add an rbd features field

Record the features values for each rbd image and each of its
snapshots.  This is really something that only becomes meaningful
for version 2 images, so this is just putting in place code
that will form common infrastructure.

It may be useful to expand the sysfs entries--and therefore the
information we maintain--for the image and for each snapshot.
But I'm going to hold off doing that until we start making
active use of the feature bits.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/Documentation/ABI/testing/sysfs-bus-rbd b/Documentation/ABI/testing/sysfs-bus-rbd
index 6fe4224..1cf2adf 100644 (file)
--- a/Documentation/ABI/testing/sysfs-bus-rbd
+++ b/Documentation/ABI/testing/sysfs-bus-rbd
@@ -25,6 +25,10 @@ client_id
 
        The ceph unique client id that was assigned for this specific session.
 
+features
+
+       A hexadecimal encoding of the feature bits for this image.
+
 major
 
        The block device major number.
@@ -78,4 +82,7 @@ snap_size
 
        The size of the image when this snapshot was taken.
 
+snap_features
+
+       A hexadecimal encoding of the feature bits for this snapshot.
 

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 8ac193f..463f8b2 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -85,6 +85,7 @@
 struct rbd_image_header {
        /* These four fields never change for a given rbd image */
        char *object_prefix;
+       u64 features;
        __u8 obj_order;
        __u8 crypt_type;
        __u8 comp_type;
@@ -148,12 +149,14 @@ struct rbd_snap {
        u64                     size;
        struct list_head        node;
        u64                     id;
+       u64                     features;
 };
 
 struct rbd_mapping {
        char                    *snap_name;
        u64                     snap_id;
        u64                     size;
+       u64                     features;
        bool                    snap_exists;
        bool                    read_only;
 };
@@ -590,6 +593,7 @@ static int rbd_header_from_disk(struct rbd_image_header *header,
                header->snap_sizes = NULL;
        }
 
+       header->features = 0;   /* No features support in v1 images */
        header->obj_order = ondisk->options.order;
        header->crypt_type = ondisk->options.crypt_type;
        header->comp_type = ondisk->options.comp_type;
@@ -632,6 +636,7 @@ static int snap_by_name(struct rbd_device *rbd_dev, const char *snap_name)
                if (!strcmp(snap_name, snap->name)) {
                        rbd_dev->mapping.snap_id = snap->id;
                        rbd_dev->mapping.size = snap->size;
+                       rbd_dev->mapping.features = snap->features;
 
                        return 0;
                }
@@ -648,6 +653,7 @@ static int rbd_dev_set_mapping(struct rbd_device *rbd_dev, char *snap_name)
                    sizeof (RBD_SNAP_HEAD_NAME))) {
                rbd_dev->mapping.snap_id = CEPH_NOSNAP;
                rbd_dev->mapping.size = rbd_dev->header.image_size;
+               rbd_dev->mapping.features = rbd_dev->header.features;
                rbd_dev->mapping.snap_exists = false;
                rbd_dev->mapping.read_only = rbd_dev->rbd_opts.read_only;
                ret = 0;
@@ -1835,6 +1841,19 @@ static ssize_t rbd_size_show(struct device *dev,
        return sprintf(buf, "%llu\n", (unsigned long long) size * SECTOR_SIZE);
 }
 
+/*
+ * Note this shows the features for whatever's mapped, which is not
+ * necessarily the base image.
+ */
+static ssize_t rbd_features_show(struct device *dev,
+                            struct device_attribute *attr, char *buf)
+{
+       struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
+
+       return sprintf(buf, "0x%016llx\n",
+                       (unsigned long long) rbd_dev->mapping.features);
+}
+
 static ssize_t rbd_major_show(struct device *dev,
                              struct device_attribute *attr, char *buf)
 {
@@ -1884,6 +1903,10 @@ static ssize_t rbd_image_id_show(struct device *dev,
        return sprintf(buf, "%s\n", rbd_dev->image_id);
 }
 
+/*
+ * Shows the name of the currently-mapped snapshot (or
+ * RBD_SNAP_HEAD_NAME for the base image).
+ */
 static ssize_t rbd_snap_show(struct device *dev,
                             struct device_attribute *attr,
                             char *buf)
@@ -1907,6 +1930,7 @@ static ssize_t rbd_image_refresh(struct device *dev,
 }
 
 static DEVICE_ATTR(size, S_IRUGO, rbd_size_show, NULL);
+static DEVICE_ATTR(features, S_IRUGO, rbd_features_show, NULL);
 static DEVICE_ATTR(major, S_IRUGO, rbd_major_show, NULL);
 static DEVICE_ATTR(client_id, S_IRUGO, rbd_client_id_show, NULL);
 static DEVICE_ATTR(pool, S_IRUGO, rbd_pool_show, NULL);
@@ -1918,6 +1942,7 @@ static DEVICE_ATTR(current_snap, S_IRUGO, rbd_snap_show, NULL);
 
 static struct attribute *rbd_attrs[] = {
        &dev_attr_size.attr,
+       &dev_attr_features.attr,
        &dev_attr_major.attr,
        &dev_attr_client_id.attr,
        &dev_attr_pool.attr,
@@ -1971,12 +1996,24 @@ static ssize_t rbd_snap_id_show(struct device *dev,
        return sprintf(buf, "%llu\n", (unsigned long long)snap->id);
 }
 
+static ssize_t rbd_snap_features_show(struct device *dev,
+                               struct device_attribute *attr,
+                               char *buf)
+{
+       struct rbd_snap *snap = container_of(dev, struct rbd_snap, dev);
+
+       return sprintf(buf, "0x%016llx\n",
+                       (unsigned long long) snap->features);
+}
+
 static DEVICE_ATTR(snap_size, S_IRUGO, rbd_snap_size_show, NULL);
 static DEVICE_ATTR(snap_id, S_IRUGO, rbd_snap_id_show, NULL);
+static DEVICE_ATTR(snap_features, S_IRUGO, rbd_snap_features_show, NULL);
 
 static struct attribute *rbd_snap_attrs[] = {
        &dev_attr_snap_size.attr,
        &dev_attr_snap_id.attr,
+       &dev_attr_snap_features.attr,
        NULL,
 };
 
@@ -2037,7 +2074,8 @@ static int rbd_register_snap_dev(struct rbd_snap *snap,
 
 static struct rbd_snap *__rbd_add_snap_dev(struct rbd_device *rbd_dev,
                                                const char *snap_name,
-                                               u64 snap_id, u64 snap_size)
+                                               u64 snap_id, u64 snap_size,
+                                               u64 snap_features)
 {
        struct rbd_snap *snap;
        int ret;
@@ -2053,6 +2091,7 @@ static struct rbd_snap *__rbd_add_snap_dev(struct rbd_device *rbd_dev,
 
        snap->id = snap_id;
        snap->size = snap_size;
+       snap->features = snap_features;
 
        return snap;
 
@@ -2123,7 +2162,7 @@ static int rbd_dev_snaps_update(struct rbd_device *rbd_dev)
                        /* We haven't seen this snapshot before */
 
                        new_snap = __rbd_add_snap_dev(rbd_dev, snap_name,
-                                       snap_id, header->snap_sizes[index]);
+                                       snap_id, header->snap_sizes[index], 0);
                        if (IS_ERR(new_snap)) {
                                int err = PTR_ERR(new_snap);